The invention relates to the field of intravascular catheters, and particularly to a catheter suitable for procedures such as angioplasty and/or stent deployment, and the like.
In percutaneous transluminal coronary angioplasty (PTCA) procedures a guiding catheter is advanced in the patient""s vasculature until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guidewire crosses a lesion to be dilated. A dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient""s coronary anatomy over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with inflation fluid one or more times to a predetermined size at relatively high pressures so that the stenosis is compressed against the arterial wall and the wall expanded to open up the vascular passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resuimes through the dilated artery and the dilatation catheter and the guidewire can be removed therefrom.
In such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate of angioplasty alone and to strengthen the dilated area, physicians now normally implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel or to maintain its patency. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded within the patient""s artery to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion. See for example, U.S. Pat. No. 5,507,768 (Lau et al.) and U.S. Pat. No. 5,458,615 (Klemm et al.), which are incorporated herein by reference. Thus, stents are used to keep open a stenosed vessel, and strengthen the dilated area by remaining inside the vessel. Instead of first using one catheter to dilate the body lumen and a second catheter to deploy the stent after the dilatation, the stent may be mounted on a balloon catheter and deployed at the same time the balloon is inflated to dilate the stenotic region.
Conventional balloon catheters for intravascular procedures, such as angioplasty and stent delivery, frequently have relatively stiff proximal shaft sections to facilitate advancement of the catheter within the patient""s body lumen and a relatively flexible distal shaft sections to facilitate passage through tortuous anatomy such as distal coronary and neurological arteries without damage to the luminal wall. Typically, there is an intermediate shaft section or junction between the relatively stiff proximal shaft section and the relatively flexible distal shaft section which provides a transition between the proximal shaft section and less flexible than the distal shaft section.
A variety of intermediate shaft or junction designs have been utilized to provide a relatively smooth transition between the stiff proximal shaft section and the flexible distal shaft section. However, it has been difficult to develop a catheter design with an intermediate catheter shaft junction which provides a smooth transition and improved flexibility and which is also leak free when utilizing high pressure inflation fluid to inflate the balloon on the distal shaft section of the catheter for dilatation or stent deployment. The present invention satisfies these and other needs.
The invention is generally directed to an intraluminal catheter system with an improved transition between a proximal shaft section and a more flexible distal shaft section which greatly facilitates advancement through tortuous anatomy.
The intraluminal catheter of the invention has an elongated proximal shaft section which transitions to a more flexible distal shaft section through an improved intermediate shaft section disposed between the proximal and distal shaft sections. An inflation lumen extends within the catheter shaft to a location spaced proximal to the distal end. A guidewire receiving lumen extends within at least the distal shaft section of the catheter. The proximal shaft section has proximal and distal ends and a portion of the inflation lumen extending therein. The distal tip of the proximal shaft section is preferably tapered distally to smaller transverse dimensions. The distal shaft section has proximal and distal ends, a port in its distal end, at least part of the guidewire receiving inner lumen extending within the distal shaft section to the port in the distal end thereof, and at least part of the inflation lumen extending within the distal shaft section to a location proximal to the distal end of the distal shaft section. An inflatable member such as a balloon is preferably provided on the distal shaft section which has an interior in fluid communication with the inflation lumen.
The intermediate or transition shaft section which extends between the proximal and distal shaft sections is provided a tubular reinforcing member with proximal and distal ends, with part of the inflation lumen extending therein and with the proximal end of the tubular reinforcing member secured to the proximal shaft section proximal to the distal, preferably tapered tip. The distal end of the tubular reinforcing member extends into the inflation within the distal shaft section. An inner tubular support member may be disposed within the tubular reinforcing member with the proximal end receiving the distal tip of the proximal shaft section and secured thereto by an adhesive or other suitable means.
An outer polymeric jacket may be provided on the proximal shaft section which preferably extends distally from the proximal shaft section over the tubular reinforcing member. Preferably, the polymeric jacket extends beyond the distal end of the tubular reinforcing member into portion of the inflation lumen of the distal shaft section. The portion of the outer jacket which extends distally beyond the distal end of the tubular reinforcing member should taper to smaller transverse dimensions.
In one embodiment of the invention the distal shaft section has an outer tubular member and an inner tubular member with a portion of the inflation lumen being defined between the exterior of the inner tubular member and the interior of the outer tubular member. In this embodiment the proximal skirt of the balloon is secured to the distal end of the outer tubular member and the distal skirt of the balloon is secured to the distal extremity of the inner tubular member.
The inner tubular member extending within the distal shaft section has proximal and distal ends, ports in the proximal and distal ends and a guidewire receiving lumen extending therein between the proximal and distal ports. The proximal end of the outer tubular member surrounds and is secured to at least part of the intermediate shaft section. The inner tubular member preferably has a helical coil disposed therein, extending along a substantial length of the tubular member. A preferred construction includes the helical coil disposed within the wall of the inner tubular member and extending proximally within the inner tubular member from the distal end of the catheter to a location within the proximal extremity spaced a short distance distal to the proximal end of the inner tubular member.
This embodiment can have a rapid exchange type or over-the-wire type constructions. In the latter instance the outer tubular member and the inner tubular members extend proximally beyond the junction to the proximal end of the catheter. The inner tubular member extends along the exterior of the relatively stiff proximal portion. The outer tubular member extends to the proximal end of the catheter disposed about the proximal shaft section and the proximal extension of the inner tubular member so as to secure the two members together. In this specific embodiment, the proximal shaft section need not have the outer jacket which extends over the tubular reinforcing member in the intermediate shaft section.
Alternatively, in the rapid exchange type catheter, the distal shaft can be formed at least in part of dual lumen construction with the inflation lumen and the guidewire receiving lumen extending side-by-side along a substantial length of the distal shaft section. In this embodiment the tubular reinforcing member of the intermediate shaft section extends into the inflation lumen and secured therein. This embodiment is otherwise similar in construction to the first described embodiment above.
The tapered distal end of the proximal shaft section is preferably secured within the proximal end of the tubular reinforcing member of the intermediate shaft section. The portion of the outer tubular member which extends proximally from the proximal end of the tubular reinforcing member completes the fluid communication between the inflation lumen of the proximal shaft section with the inner lumen of the tubular reinforcing member and the portion of the inflation lumen in the distal shaft section. This construction provides enhanced flexibility to the junction between the proximal and distal shaft sections and prevents the tapered distal tip from traumatically engaging the lining of the body lumen through which the catheter passes. This embodiment may include a proximal portion of the distal shaft section with a dual lumen type construction and a distal portion of a concentric type construction with an inner tubular member and an outer tubular member as previously described.
The proximal shaft section is relatively stiff and preferably is formed from a metallic material such as stainless steel, NITINOL, MP35N, Elgiloy or other suitable high strength materials from which small diameter tubing can be readily formed. The intermediate shaft section is of intermediate stiffness and the components are formed of high strength polymeric materials such as PEEK. polyimide and the like. The outer tubular member of the distal shaft section is formed of a lower strength polymeric material such as high density polyethylene, polyamide or the like. The inner tubular member of the distal shaft section is formed from a lubricious material such as high density polyethylene and the helical coil within the inner tubular member is formed of conventional metallic materials such as stainless steel and radiopaque metals such as platinum, tantalum and alloys thereof. The inner tubular member may be of multilayered construction with the helical coil disposed between the layers.
The catheter of the present invention provides an improved design with superior pushability in the proximal shaft section, a greater degree of flexibility in the distal shaft section for more distal advancement of the catheter and an intermediate shaft section with a smoother, more flexible transition between the proximal and distal shaft sections.
These and other advantages of the invention will become more apparent from the following detailed description of the invention and the accompanying exemplary drawings.